Insulation

Abstract

The present invention provides a thermal insulation material that includes a thermal insulation layer capable of suppressing thermal conductivity even when prepared from a slurry containing silica particles in an aqueous solvent. [Solution] Silica particles and the following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A thermal insulation material is provided which includes a thermal insulation layer containing a surfactant that satisfies the following conditions. Here, the surface tension is the surface tension measured by the Dunou method using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The light transmittance is the light transmittance measured by a spectrophotometer using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution.

Description

Technical Field

[0001] The present invention relates to a heat insulating material.

Background Art

[0002] As a power source for electric vehicles such as hybrid vehicles and electric vehicles, portable electronic devices such as portable terminals, mobile phones and notebook personal computers, and wearable devices, non-aqueous electrolyte secondary batteries such as lithium ion batteries are widely used. For example, in modules and packs of lithium ion batteries mounted in electric vehicles and the like, since a plurality of cells are stacked, heat insulating materials for preventing adjacent cells from directly contacting each other and further insulating between cells may be disposed between the cells. For example, Patent Document 1 describes a heat insulating material having a heat insulating layer containing silicon dioxide particles and inorganic fibers, and a method for producing a heat insulating material including obtaining a heat insulating layer by applying and molding a mixed solution prepared by mixing silicon dioxide particles and inorganic fibers with a solvent.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method of manufacturing an insulating layer by applying and molding the above-mentioned mixture, the example in Patent Document 1 uses a solvent containing an organic solvent (a mixed solvent of acetic acid / water or acetic acid solvent) as the solvent for the mixture. On the other hand, in recent years, there has been a demand to reduce the amount of organic solvents used from the viewpoint of environmental considerations and sustainable production by reducing dependence on natural resources such as petroleum. However, if the organic solvent contained in the solvent of the above-mentioned mixture is changed to water, the thermal conductivity of the insulating layer obtained from the mixture tends to increase, and the insulating performance tends to decrease. If a technology is provided that can suppress the thermal conductivity even when using water as the solvent when producing an insulating layer from a slurry containing silica particles in the solvent, more environmentally friendly technologies and production methods can be adopted.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a thermal insulation material including a thermal insulation layer that can suppress thermal conductivity even when prepared from a slurry containing silica particles in an aqueous solvent. Another related object is to provide a method for producing a thermal insulation material, which includes obtaining a thermal insulation layer from the slurry containing the above-mentioned silica particles in an aqueous solvent. [Means for solving the problem]

[0006] This specification specifies silica particles and the following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A thermal insulation material is provided which includes a thermal insulation layer containing a surfactant that satisfies the above requirements. Here, the surface tension is the surface tension measured by the Dunouy method using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The light transmittance is the light transmittance measured by a spectrophotometer using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The thermal insulation layer containing silica particles and a surfactant that satisfies the above requirements can suppress thermal conductivity even when prepared from a slurry containing these in an aqueous solvent. This promotes the use of water instead of organic solvents in the manufacture of the thermal insulation layer and the thermal insulation material containing the thermal insulation layer, thereby reducing the amount of organic solvents used. The content of the surfactant in the thermal insulation layer can be, for example, in the range of 0.01 parts by mass or more and 15 parts by mass or less per 100 parts by mass of silica particles.

[0007] The HLB (hydrophile-lipophile balance) value of the above-mentioned surfactant is preferably 10 or less. The techniques disclosed herein can be suitably carried out using surfactants with an HLB value of 10 or less.

[0008] As the surfactant mentioned above, for example, a nonionic silicone-based surfactant can be preferably used. The technology disclosed herein can be suitably carried out using a nonionic silicone-based surfactant.

[0009] In some preferred embodiments, the BET specific surface area of ​​the silica particles is 80 m². 2 / g or more 400m 2 The value is less than or equal to / g. The techniques disclosed herein can be suitably carried out using silica particles having a BET specific surface area within the above range.

[0010] For example, hydrophilic fumed silica can be used as the silica particles. The technology disclosed herein can be preferably applied to an insulating layer containing hydrophilic fumed silica.

[0011] The above-mentioned insulation layer may further contain inorganic fibers. Inorganic fibers can help improve the ease of manufacturing (e.g., ease of molding), improve thickness accuracy, and improve strength of the insulation layer.

[0012] The thermal insulation layer and thermal insulation material including the thermal insulation layer disclosed herein can be preferably used, for example, in a battery module or battery pack including a plurality of arranged cells, in which they are positioned between adjacent cells, taking advantage of their ability to exhibit good thermal insulation properties.

[0013] Furthermore, this specification provides a method for manufacturing a thermal insulation material. The method includes a mixing step of mixing silica particles and a surfactant that satisfies a surface tension of 15 mN / m to 30 mN / m and a light transmittance of 90% or less at a wavelength of 400 nm in an aqueous solvent to obtain a mixed solution; a coating step of applying the mixed solution obtained in the mixing step to obtain a coating film; and a molding step of molding the coating film obtained in the coating step to obtain a thermal insulation layer. According to this manufacturing method, a thermal insulation layer with suppressed thermal conductivity can be produced while using water (aqueous solvent) as the solvent in the mixing step. This promotes the use of water instead of organic solvents in the manufacture of the thermal insulation layer and thermal insulation materials containing the thermal insulation layer, thereby reducing the amount of organic solvents used.

[0014] In some embodiments, the content of the surfactant in the mixture can be, for example, in the range of 0.05 parts by mass or more and 20 parts by mass or less per 100 parts by mass of silica particles. The techniques disclosed herein can preferably be carried out using the surfactant in such a content as described above.

[0015] Furthermore, combinations of the elements described herein may also be included within the scope of the invention for which patent protection is sought in this patent application. [Brief explanation of the drawing]

[0016] [Figure 1]This is a schematic perspective view showing an example of a battery module in which thermal insulation material according to one embodiment is arranged between cells. [Figure 2] This is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] This is a schematic cross-sectional view showing a thermal insulation material according to one embodiment. [Modes for carrying out the invention]

[0017] Preferred embodiments of the present invention are described below. Matters other than those specifically mentioned herein but necessary for carrying out the present invention can be understood by those skilled in the art based on the teachings on carrying out the invention described herein and the common technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed herein and the common technical knowledge in the art. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals and described accordingly, and redundant descriptions may be omitted or simplified. Also, the embodiments shown in the drawings are schematic for the purpose of clearly illustrating the present invention and do not necessarily accurately represent the size or scale of the actual product provided.

[0018] In this specification, "weight" and "mass" may be interpreted as interchangeable. For example, "weight%" and "mass%" may be interpreted as interchangeable, and "parts by weight" and "parts by mass" may be interpreted as interchangeable.

[0019] In this specification, "surface tension" of a surfactant means the surface tension measured by the Dunouy method at a temperature of 20°C using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The surface tension of a surfactant can be measured using a commercially available surface tension measuring device. As the surface tension measuring device, for example, the surface tension measuring device manufactured by Kyowa Interface Science Co., Ltd., trade name "Wilhelmy type surface tension meter" or an equivalent product can be used. More specifically, the surface tension of a surfactant is measured by the method described in the examples below.

[0020] In this specification, "light transmittance at a wavelength of 400 nm" of a surfactant means the light transmittance at a wavelength of 400 nm measured by a spectrophotometer using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. In this specification, when simply referred to as "light transmittance," unless otherwise specified or clear from the context, the above light transmittance refers to the light transmittance at a wavelength of 400 nm. A commercially available spectrophotometer can be used; for example, a UV-Vis spectrophotometer manufactured by Shimadzu Corporation, trade name "SolidSpec3700," or an equivalent product can be used. More specifically, the light transmittance of the surfactant is measured by the method described in the examples below.

[0021] In this specification, “water solvent” means a solvent that consists substantially of water and, at least in intent, does not use organic solvents. The above-mentioned water solvent is typically a solvent in which the organic solvent content is less than 5% by mass (preferably less than 3% by mass, less than 1% by mass, less than 0.5% by mass, or less than 0.1% by mass), and is a concept that encompasses solvents consisting only of water (solvents that do not use organic solvents, i.e., organic solvent-free solvents).

[0022] <Insulation layer> (Silica particles) The thermal insulation material disclosed herein has a thermal insulation layer containing silica particles. Silica (SiO2) can be classified into crystalline silica, amorphous silica, etc., based on its structural characteristics, and into natural silica, synthetic silica, etc., depending on how it is obtained. Synthetic silica can be classified into dry silica, wet silica, silica aerogel, etc., depending on the manufacturing method. Dry silica can be classified into silica obtained by combustion, silica obtained by arc, etc., and wet silica can be classified into silica obtained by gel, silica obtained by sedimentation, etc. The type of silica particles used as a component of the thermal insulation layer is not particularly limited and may be silica particles of any of the above types. In some embodiments, dry silica is preferred as the silica particles, fumed silica is more preferred among dry silica, and hydrophilic fumed silica is particularly preferred among fumed silica.

[0023] Hydrophilic fumed silica refers to fumed silica that mainly has hydrophilic silanol groups (Si-OH) on its surface, and generally refers to fumed silica in which the silanol groups have not been replaced with hydrophobic groups by surface treatment or the like. Typically, the above surface treatment requires a coupling reaction at high temperatures. Therefore, by using hydrophilic fumed silica that does not require the above surface treatment (hydrophobic treatment) as fumed silica, it is possible to save the energy required to obtain the raw material for the heat insulating layer, and consequently reduce the environmental burden of obtaining that energy. Furthermore, hydrophilic fumed silica has a stronger interaction with water than hydrophobic fumed silica, and is more prone to aggregation (reduction of interparticle distance) when organic solvents are replaced with water. Therefore, it is particularly significant to suppress the aggregation by applying the technology disclosed herein.

[0024] Silica particles generally exist as primary particles, as aggregates formed by the aggregation of primary particles, or as concentrated particles formed by further aggregation of aggregates. In an insulating layer, silica particles may be dispersed as primary particles, as aggregates, as concentrated particles, or in combination of these states.

[0025] The average primary particle diameter of silica particles is not particularly limited, but is, for example, about 1 nm to 100 nm, preferably 2 nm or more, more preferably 4 nm or more, also preferably 80 nm or less, more preferably 40 nm or less, even more preferably 30 nm or less, and particularly preferably 20 nm or less. When the silica particles include fumed silica, the average primary particle diameter of the fumed silica is, for example, about 1 nm to 40 nm, preferably 2 nm or more, more preferably 4 nm or more, also preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. When the average primary particle diameter of silica particles is within the above range, it is easier to ensure good thermal insulation. Methods for determining the average primary particle diameter of silica particles include measurement using an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, one method is to randomly select silica particles that appear on the electron microscope, measure their particle diameter, and calculate the average value of those values. Regarding particle size, if the particle is spherical, its diameter may be used; if the particle observed under an electron microscope is elliptical, the midpoint between its short and long axes may be used; and if the particle is irregularly shaped, the midpoint between its short and long sides may be used.

[0026] The average particle diameter of secondary aggregates of silica particles (aggregates of primary particles) is not particularly limited and is usually between 0.1 μm and 100 μm, but is preferably 1 μm or more, more preferably 2 μm or more, preferably 90 μm or less, and more preferably 80 μm or less. A method for determining the average particle diameter of secondary aggregates of silica particles is to measure it using the same method as for the primary particle diameter.

[0027] The BET specific surface area of the silica particles is not particularly limited, and for example, it may be about 40 m 2 / g or more and 800 m 2 / g or less, and may be about 60 m 2 / g or more and 600 m 2 / g or less. In some embodiments, the BET specific surface area of the silica particles is preferably 90 m 2 / g or more and less than 380 m 2 / g, more preferably 130 m 2 / g or more, still more preferably 175 m 2 / g or more, and even more preferably 200 m 2 / g or more, and preferably 350 m 2 / g or less, more preferably 320 m 2 / g or less, and even more preferably 300 m 2 / g or less. When the BET specific surface area of the silica particles is within the above range, it is easier to ensure good heat insulation even under high temperature and high humidity conditions. The BET specific surface area can be measured by the multi-point nitrogen adsorption method (BET method) in accordance with ISO 5794 / 1 of the International Organization for Standardization. For example, the "AEROSIL 380" manufactured by Evonik has a nominal BET specific surface area of 380 m 2 / g, and considering the error, it is expressed as 350 m 2 / g to 410 m 2 / g. In this case, in this specification, it is considered based on the nominal value of 380 m 2 / g.

[0028] The apparent specific gravity of silica particles is not particularly limited and may be, for example, 30 g / L to 130 g / L, preferably 40 g / L or more (e.g., 50 g / L or more), and preferably 120 g / L or less (e.g., 100 g / L or less). In some embodiments, the apparent specific gravity of silica particles may be, for example, 80 g / L or less, or 60 g / L or less. The apparent specific gravity of silica particles can be determined by filling the silica particles into a container capable of measuring volume, such as a 250 mL graduated cylinder, measuring the filling mass (X g) and filling volume (Y mL), and dividing the filling mass by the filling volume ([Apparent specific gravity (g / L)] = X / Y × 1000). If a nominal value of the apparent specific gravity is provided by the manufacturer, that nominal value may be adopted.

[0029] Commercially available silica particles include hydrophilic fumed silica such as the AEROSIL series (manufactured by Nippon Aerosil Co., Ltd.) AEROSIL50, 90, 130, 200, 200V, 300, and 380; the Rheoroseal series (manufactured by Tokuyama Corporation) QS-09, QS-10, QS-102, QS-20, QS-20L, QS-30, QS-40, and CP-102; the HDK series (manufactured by Asahi Kasei Wacker Silicon Co., Ltd.) HDKV15, N20, T30, and T40; hydrophobic fumed silica such as the AEROSIL series (manufactured by Nippon Aerosil Co., Ltd.) AEROSIL R972 and R976S; the HDK series (manufactured by Asahi Kasei Wacker Silicon Co., Ltd.) HDK H15, H20, and H30; and silica aerogel such as Airica (manufactured by Tokuyama Corporation). The insulating layer may contain one type of silica particle, or it may contain two or more types of silica particles.

[0030] The silica particle content in the thermal insulation layer is not particularly limited and may be, for example, in the range of 50% to 99.5% by mass. In some embodiments, the content is preferably 60% or more by mass, more preferably 70% or more by mass, and may also be 75% or more by mass, and preferably 95% or less by mass, more preferably 90% or less by mass, even more preferably 85% or less by mass, and may also be 80% or less by mass. A thermal insulation layer with a silica particle content within any of the above ranges makes it easier to ensure good thermal insulation.

[0031] (Surfactants) The thermal insulation layer in the technology disclosed herein contains a surfactant that satisfies the following conditions: a surface tension of 15 mN / m or more and 30 mN / m or less; and a light transmittance of 90% or less at a wavelength of 400 nm. With a surfactant that satisfies the above surface tension and light transmittance requirements, when a thermal insulation layer is prepared using a mixture containing thermal insulation layer constituent materials such as silica particles in a solvent (typically a slurry in which the thermal insulation layer constituent materials are dispersed in the solvent), the thermal conductivity of the resulting thermal insulation layer can be suppressed even when water is used as the solvent. For example, even if the organic solvent contained in the solvent of the mixture in the conventional technology is replaced with water, the decrease in thermal insulation performance due to the effect of the replacement can be suppressed. This makes it possible to promote the use of water instead of organic solvents in the manufacture of the thermal insulation layer and thermal insulation materials containing the thermal insulation layer, and to reduce the amount of organic solvent used.

[0032] In the technology disclosed herein, even if the solvent in the mixture is water, the reason why the thermal conductivity of the insulating layer obtained from the mixture is suppressed is that the use of a surfactant that satisfies the above requirements suppresses excessive aggregation (reduction in the distance between particles) of the silica particles in the mixture when the mixture containing silica particles in the water solvent dries, and an insulating layer having more pores of a size suitable for improving thermal insulation (for example, suppression of heat transfer due to gas convection in the insulating layer) is formed. In other words, since the surface tension of water is generally higher than that of organic solvents, simply replacing the organic solvent constituting the solvent of the mixture with water tends to promote aggregation of silica particles during drying due to the increase in surface tension. However, by using the surfactant, the aggregation of silica particles can be suppressed, and the decrease in the amount of pores of a size suitable for improving thermal insulation (for example, the volume of pores of the above size contained per unit mass of the insulating layer) can be suppressed, resulting in a suppression of the thermal conductivity of the obtained insulating layer. Note that the technology disclosed herein is not limited to the above considerations.

[0033] The surface tension of the surfactant may be less than 30 mN / m, or 29 mN / m or less. In some embodiments, the surface tension of the surfactant is appropriately 28 mN / m or less, preferably 27 mN / m or less, more preferably 25 mN / m or less, and may also be 23 mN / m or less, 22 mN / m or less, or 21 mN / m or less. Surfactants with lower surface tension can more efficiently suppress the increase in thermal conductivity associated with replacing organic solvents with aqueous solvents. For example, the same effect can be obtained with a smaller amount of surfactant, or a higher effect can be obtained with the same amount of surfactant used. In addition, in some embodiments, the surface tension of the surfactant may be greater than 15 mN / m, 16 mN / m or more, 18 mN / m or more, 19 mN / m or more, or 20 mN / m or more, from the viewpoint of the availability and cost of the surfactant.

[0034] In the technologies disclosed herein, the light transmittance of a surfactant (i.e., the light transmittance of an aqueous solution containing the surfactant at a concentration of 1.1% by mass) has technical significance as an indicator of the affinity between the surfactant and water. Surfactants with a light transmittance of 90% or less tend to exhibit an effect of suppressing the aggregation of silica particles when a mixture containing silica particles in an aqueous solvent dries, due to their moderately limited affinity for water. The light transmittance of the surfactant may be 89% or less, 88% or less, or 87% or less. In some embodiments, the light transmittance of the surfactant is preferably 85% or less, more preferably 82% or less, may be 80% or less, may be 75% or less, may be 70% or less or 65% or less, may be 60% or less, 55% or less, 50% or less, 45% or less, or 40% or less. Furthermore, the light transmittance of the surfactant may be, for example, 5% or more, 7% or more, or 10% or more. In some embodiments, from the viewpoint of ease of preparation and stability of the mixture, it is appropriate to have 15% or more, preferably 20% or more, may be 25% or more, may be 30% or more, or may be 35% or more.

[0035] In some embodiments, the surfactant may preferably satisfy at least one of the following conditions: (A) surface tension is 15 mN / m or more and 25 mN / m or less; and (B) light transmittance is 75% or less (for example, 20% or more and 75% or less). By using a surfactant that satisfies either or both of the above conditions (A) and (B), the effect of suppressing the increase in thermal conductivity associated with the replacement of an organic solvent with an aqueous solvent can be achieved more efficiently.

[0036] The surfactants used in the technologies disclosed herein are not particularly limited, as long as they satisfy the above-mentioned surface tension and light transmittance requirements. For example, nonionic surfactants that satisfy the above requirements can be preferably used. Surfactants that satisfy the above requirements can be preferably selected from, for example, silicone-based surfactants. The technologies disclosed herein can preferably be carried out using a surfactant that satisfies either or both of the following conditions: (i) being a nonionic surfactant and (ii) being a silicone-based surfactant (for example, a nonionic silicone-based surfactant) that also satisfies the above-mentioned surface tension and light transmittance requirements.

[0037] In this specification, a silicone-based surfactant refers to a surfactant containing a compound having a siloxane bond (silicone compound) as an active ingredient. The silicone compound may, for example, have a structure in which a hydrophilic structure is introduced into the main chain and / or side chain of a compound having a siloxane bond as its main skeleton. The hydrophilic structure can be introduced, for example, by modifying a compound having a siloxane bond as its main skeleton (typically a polyorganosiloxane such as polydimethylsiloxane) by, for example, polyether modification, polyester modification, or polyglycerin modification. The polyether modification is a modification that introduces a polyoxyalkylene structure such as a polyoxyethylene structure or a polyoxypropylene structure, and it is preferable that the modification introduces a polyoxyethylene structure. In addition to the hydrophilic structure described above, the silicone compound may also have a lipophilic structure (for example, an alkyl group, preferably an alkyl group having about 3 to 12 carbon atoms) introduced into it.

[0038] The HLB value of the surfactant described above may be, for example, approximately 16 or less, 14 or less, or 12 or less. In some embodiments, the HLB value of the surfactant is appropriately 10 or less, preferably 8.0 or less, may be 6.0 or less, may be 5.0 or less or 4.0 or less, or may be 3.0 or less (for example, 2.8 or less or 2.5 or less). Also in some embodiments, the HLB value of the surfactant is appropriately 0.5 or less, preferably 1.0 or more, may be 1.5 or more, or may be 2.0 or more. The surfactant in the technology disclosed herein may preferably have an HLB value that satisfies any of the above upper and lower limits. The HLB value of the surfactant can be calculated by the Kawakami method based on the molecular structure of the surfactant, specifically by the following formula: HLB = 7 + 11.7 log(Mw × Mo); In the above formula, Mw represents the molecular weight of the hydrophilic group, and Mo represents the molecular weight of the lipophilic group. If the manufacturer or other source provides a nominal molecular weight, that nominal value may be used.

[0039] The molecular weight of the surfactant described above is not particularly limited and may be in the range of approximately 250 to 10000. In some embodiments, the molecular weight of the surfactant is suitable to be, for example, 500 or more, advantageous to be 700 or more, preferably 800 or more, may be 900 or more, may be 1000 or more, or may be 1100 or more or 1200 or more. In some embodiments, the molecular weight of the surfactant is suitable to be, for example, 8000 or less, advantageous to be 7000 or less, preferably 6000 or less, and more preferably 5000 or less. Surfactants having such molecular weights are likely to yield the surface tension and light transmittance described above. The molecular weight of the surfactant can be the weight-average molecular weight based on GPC (gel permeation chromatography) or the molecular weight calculated as the sum of atomic weights from the chemical structure. If a nominal molecular weight is provided by the manufacturer, that nominal value may be adopted.

[0040] The amount of surfactant in the insulating layer is not particularly limited. The amount of surfactant in the insulating layer may be, for example, 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 12 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, or 6 parts by mass or less, per 100 parts by mass of silica particles contained in the insulating layer. If the amount of surfactant in the insulating layer is too high, the thermal conductivity of the insulating layer may tend to increase. Furthermore, the amount of surfactant in the insulating layer may be, for example, 0.001 parts by mass or more, per 100 parts by mass of silica particles contained in the insulating layer. From the viewpoint of easily obtaining a higher usage effect, it is advantageous to have 0.01 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 1.0 part by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, or 5.0 parts by mass or more.

[0041] In some embodiments, the content of the surfactant in the insulating layer may be, for example, 20% by mass or less or less than 20% by mass of the insulating layer, usually 18% by mass or less is appropriate, preferably 12% by mass or less, more preferably less than 12% by mass, and may be 8.5% by mass or less, 7% by mass or less, 5% by mass or less, or 4.5% by mass or less. If the content is too high, the thermal conductivity of the insulating layer may tend to increase. Also in some embodiments, the content of the surfactant in the insulating layer may be, for example, 0.001% by mass or more, and from the viewpoint of easily obtaining a higher usage effect, it is advantageous to be 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.8% by mass or more, may be 1.5% by mass or more, may be 2.5% by mass or more, or may be 3.5% by mass or more or 4.0% by mass or more.

[0042] The surfactant content in the insulation layer can be determined by extracting the surfactant from the insulation layer using a suitable solvent (a solvent capable of dissolving the target surfactant) and performing quantitative analysis using a known method. Furthermore, the type of surfactant contained in the insulation layer can be determined by similarly extracting the surfactant from the insulation layer using a suitable solvent and identifying the surfactant contained in the resulting extract using a known method. It should be noted that the surfactant contained in the insulation layer can be considered as the residual amount of surfactant used during the manufacture of the insulation material.

[0043] (Inorganic fibers) The thermal insulation layer in the technology disclosed herein may further contain inorganic fibers in addition to the silica particles and surfactant described above. The inorganic fibers can help improve the ease of manufacturing the thermal insulation layer (e.g., ease of molding), improve thickness accuracy, and improve the strength of the thermal insulation layer. The type of inorganic fiber is not particularly limited. Examples of inorganic fibers that can be preferably used from the viewpoint of heat resistance and strength include glass fibers, silica fibers, alumina fibers, silica-alumina fibers, silica-alumina-magnesia fibers, biosoluble inorganic fibers, zirconia fibers, alkaline earth metal silicate (alkaline earth silicate (AES)) fibers, glass wool, rock wool, and basalt fibers. The thermal insulation layer may contain one type of inorganic fiber or two or more types of inorganic fibers.

[0044] In embodiments in which the thermal insulation layer includes inorganic fibers, the content of inorganic fibers in the thermal insulation layer is not particularly limited and may be, for example, 0.5% to 50% by mass, preferably 1% or more by mass, more preferably 3% or more by mass, even more preferably 5% or more by mass, and also preferably 40% or less by mass, more preferably 35% or less by mass, and even more preferably 30% or less by mass. When the fiber content is within the above range, it becomes easier to ensure good thermal resistance and to manufacture the thermal insulation layer.

[0045] The average fiber length of the inorganic fibers is not particularly limited and may be, for example, 0.05 mm to 50 mm, preferably 0.5 mm or more, more preferably 1.0 mm or more, even more preferably 2 mm or more, and may also be 4 mm or more or 5 mm or more, and preferably 25 mm or less, more preferably 13 mm or less, even more preferably 10 mm or less, and may also be 8 mm or less, or 6 mm or less. When the average fiber length of the fibers is within the above range, it is easier to suitably achieve both ease of manufacturing and strength of the heat insulating layer.

[0046] The average fiber diameter of the inorganic fibers is not particularly limited and may be, for example, 0.1 μm to 50 μm, preferably 1 μm or more, more preferably 5 μm or more, even more preferably 7 μm or more, and also preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. When the average fiber diameter of the fibers is within the above range, it is easier to ensure good thermal insulation and mechanical strength.

[0047] In some embodiments, the inorganic fibers preferably include inorganic fibers with a fiber length of 6 mm or more and less than 35 mm. The proportion of inorganic fibers with a fiber length of 6 mm or more and less than 35 mm among the total number of inorganic fibers contained in the insulating layer is not particularly limited, and may be, for example, 30% to 100%, preferably 95% or less, preferably 35% or more, more preferably 40% or more, and even more preferably 50% or more. When the content of inorganic fibers having the above fiber length is within the above range, it becomes easier to ensure good heat insulation and mechanical strength.

[0048] In embodiments in which the thermal insulation layer includes inorganic fibers, the mass ratio (silica particles:inorganic fibers) of silica particles to inorganic fibers contained in the thermal insulation layer is not particularly limited and may be in the range of, for example, 40:60 to 99:1. From the viewpoint of easily ensuring a good balance between thermal insulation and mechanical strength, in some embodiments, the above mass ratio (silica particles:inorganic fibers) is suitable to be, for example, 45:55 or more, preferably 50:50 or more, more preferably 60:40 or more, even more preferably 70:30 or more, and may also be 80:20 or more (for example 82:18 or more), and may also be suitable to be, for example 98:2 or less, preferably 95:5 or less, may also be 90:10 or less, and may also be 88:12 or less.

[0049] (Other ingredients) The above-mentioned insulating layer may contain other components as needed. Specific examples of other components include binders, inorganic particles other than silica particles, and organic fibers.

[0050] The binder can help improve the shape stability and strength of the insulation layer. In embodiments in which the insulation layer contains a binder, the type of binder is not particularly limited and may be an organic binder or an inorganic binder. Specific examples of organic binders include thermoplastic resins, thermoplastic elastomers, thermosetting resins, thermosetting elastomers, sugars, and water-soluble polymers. Specific examples of inorganic binders include aluminum oxide, zirconium oxide, magnesium oxide, titanium oxide, and calcium oxide. From the viewpoint of heat resistance and flame resistance, inorganic binders are generally more advantageous than organic binders. The insulation layer may contain one type of binder, or two or more types of binders, or it may substantially contain no binder at all.

[0051] The binder content in the insulating layer is not particularly limited and can be set appropriately to obtain the desired effect. In some embodiments, the binder content in the insulating layer may be, for example, 0.01% to 10% by mass of the insulating layer, and may be 0.05% or more, 0.1% or more by mass, or 0.2% or more by mass from the viewpoint of shape stability and ease of molding. In some embodiments, the binder content (especially organic binder) in the insulating layer is preferably 5% or less by mass, more preferably 3% or less by mass, and even more preferably 1% or less by mass, from the viewpoint of the mechanical strength of the insulating layer in the high-temperature range.

[0052] The insulating layer may contain inorganic particles other than silica particles. Examples of inorganic particles other than silica include zinc oxide, aluminum oxide, titanium oxide particles, silicon carbide particles, ilmenite particles (FeTiO), zirconium silicate particles, iron(III) oxide particles, iron(II) (wustite (FeO) particles, magnetite particles (Fe3O4), hematite particles (Fe2O3)), chromium dioxide particles, zirconium oxide particles, manganese dioxide particles, zirconia sol, titania sol, silica sol, alumina sol, bentonite particles, kaolin particles, etc. In some embodiments, the above-mentioned descriptions regarding the average particle diameter and BET specific surface area of ​​silica particles can also be applied to the average particle diameter (primary average particle diameter, average particle diameter of secondary aggregates) and BET specific surface area of ​​inorganic particles other than silica particles.

[0053] Other examples of inorganic particles besides silica particles include carbon-based particles such as graphite, carbon black, and carbon powder. Graphite with a particle size of 18 μm or less is preferred. The particle size of graphite is measured in the same manner as the mean primary particle size of silica particles. If a manufacturer provides a nominal particle size, that nominal value may be used. Graphite can be in various shapes, including flake, scale, and spherical. Examples of commercially available flake graphite include BF-3AK, FBF, and BF-10AK from Chuetsu Graphite Industry Co., Ltd., and GE-1, Z-5F, CNP7, and V-10F from Ito Graphite Industry Co., Ltd. Examples of commercially available scale graphite include HLP and SB-1 from Chuetsu Graphite Industry Co., Ltd. Examples of commercially available spheroidal graphite include SG-BH8 from Ito Graphite Industry Co., Ltd. Commercially available carbon black products include TOKABLACK #5500 from Tokai Carbon Co., Ltd. and MA100 from Mitsubishi Chemical Corporation. Although not particularly limited, in some embodiments in which carbon black is used as inorganic particles, carbon black with a relatively high DBP oil absorption rate is generally preferred from the viewpoint of reducing thermal conductivity. The DBP oil absorption rate is appropriately 40 mL / 100 g or more, and preferably 60 mL / 100 g or more or 80 mL / 100 g or more.

[0054] The thermal insulation material may contain only one type of inorganic particle other than silica particles, or it may contain two or more types. In some embodiments, the inorganic particles other than silica particles are preferably inorganic particles that can suppress thermal radiation, and more specifically, they are preferably inorganic particles that have an absorption peak in the infrared region.

[0055] In the thermal insulation material disclosed herein, the proportion of silica particles among the inorganic particles contained in the thermal insulation layer is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 85% by mass or more, 90% by mass or more, or 95% by mass or more. The inorganic particles may consist substantially of silica particles. Here, "substantially" means that, at least intentionally, no inorganic particles other than silica particles are included, but it is not prohibited that inorganic particles other than silica particles may be unintentionally included as impurities or crushed material of other components.

[0056] In some embodiments, the insulation layer may contain organic fibers. Specific examples of organic fibers include felt made of cellulose fiber, polyester, polypropylene, etc. It is preferable to use organic fibers in combination with inorganic fibers. The content of organic fibers in the insulation layer can be appropriately set to obtain the desired effect, and may be, for example, 0.01% by mass or more, 0.5% by mass or more, or 3% by mass or more, or 20% by mass or less, 10% by mass or less, or 5% by mass or less. In some embodiments, from the viewpoint of heat resistance, etc., the content of organic fibers in the insulation layer is preferably less than 3% by mass, more preferably less than 1% by mass, and may be less than 0.1% by mass or less than 0.01% by mass. An insulation layer that substantially does not contain organic fibers is also possible.

[0057] In some embodiments, the heat insulating layer may further contain a surfactant that does not satisfy the above-mentioned surface tension and light transmittance requirements (hereinafter also referred to as an optional surfactant) in addition to the surfactant that satisfies these requirements. The optional surfactant may be useful, for example, for improving the ease of preparation of a mixture containing silica particles in an aqueous solvent, improving handling (e.g., improving fluidity), improving dispersion stability (e.g., suppressing viscosity changes over time), and improving moldability when forming the heat insulating layer from the mixture. When using an optional surfactant, the amount used should, for example, be 80% by mass or less, preferably 60% by mass or less, and may also be 50% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. The optional surfactant may not be used at all.

[0058] (Creation of an insulating layer) The method for producing the heat insulating layer disclosed herein is not particularly limited and can be produced by appropriately employing known processes. For example, a mixture containing silica particles and a surfactant satisfying the above requirements, and further containing other optional components (such as inorganic fibers) as needed, can be prepared by known mixing methods such as wet or dry methods, and a heat insulating layer can be produced using this mixture. A preferred method for producing the heat insulating layer disclosed herein includes a method in which the above mixture (typically a slurry-like mixture) is prepared by a wet method.

[0059] A method for producing an insulating layer, which includes preparing the above-mentioned mixture by a wet method, is one that includes, for example, the following steps. • Mixing step: A step of mixing silica particles, a surfactant that satisfies the above requirements, and other optional components (such as inorganic fibers) that may be used as needed, in a solvent to obtain a mixed solution. • Coating process: A process of applying the above mixture to obtain a coated film. • Molding process: A process of molding the above-mentioned coated film to obtain a heat insulating layer.

[0060] Mixing in the mixing process can be carried out using, for example, a disper, laboplast mill, trimix, planetary mixer, kneader, etc.

[0061] The type of solvent is not particularly limited. The heat insulating layer disclosed herein contains a surfactant that satisfies the above requirements, and in embodiments where water is used as the solvent, the thermal conductivity of the resulting heat insulating layer can be suppressed. Taking advantage of this feature, the heat insulating layer disclosed herein can preferably be manufactured in embodiments where water is used as the solvent. Accordingly, this specification provides a method for manufacturing a heat insulating layer, comprising: a mixing step of mixing silica particles and a surfactant that satisfies a surface tension of 15 mN / m or more and 30 mN / m or less and a light transmittance of 90% or less in water to obtain a mixed solution; a coating step of applying the mixed solution obtained in the mixing step to obtain a coated film; and a molding step of molding the coated film obtained in the coating step to obtain a heat insulating layer. The heat insulating material disclosed herein may include a heat insulating layer manufactured by the above method.

[0062] In an embodiment in which an aqueous solvent is used as the solvent for the above mixture, the concentration of the surfactant in the aqueous solvent may be, for example, 0.001% by mass or more, and from the viewpoint of easily obtaining a higher usage effect, it is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, may be 0.3% by mass or more, may be 0.5% by mass or more, may be 0.8% by mass or more, or may be 1.0% by mass or more. The concentration of the surfactant in the aqueous solvent may be, for example, 10% by mass or less, may be 7.0% by mass or less, may be 5.0% by mass or less, may be 4.0% by mass or less, may be 3.0% by mass or less, or may be 2.0% by mass or less. The concentration [by mass] of the surfactant in the aqueous solvent can be calculated by the following formula: (mass of surfactant contained in the mixture) / (mass of aqueous solvent contained in the mixture) × 100;

[0063] The amount of the surfactant added to the mixture in the mixing process is not particularly limited and can be appropriately set considering the balance between the effect of use and the influence on other properties. In some embodiments, the amount of the surfactant added to the mixture may be, for example, 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, or 6 parts by mass or less, based on 100 parts by mass of silica particles contained in the mixture. If the amount of the surfactant added is too high, the thermal conductivity of the resulting insulating layer may tend to increase. Furthermore, the amount of the surfactant added to the mixture may be, for example, 0.001 parts by mass or more, based on 100 parts by mass of silica particles contained in the mixture. From the viewpoint of easily obtaining a higher effect of use, it is advantageous to have 0.01 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 1.0 part by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, or 5.0 parts by mass or more.

[0064] The mixing temperature is not particularly limited, but is usually 20°C or higher and below the boiling point of the solvent, preferably 22°C or higher, more preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. When the mixing temperature is within the above range, the solvent (e.g., organic solvent) is less likely to volatilize, and the mixing ratio is less likely to change.

[0065] The mixing time is not particularly limited, but is usually between 1 minute and 5 hours, preferably 5 minutes or more, preferably 4 hours or less, more preferably 2 hours or less, and even more preferably 1 hour or less. When the mixing time is within the above range, an insulating layer can be efficiently produced.

[0066] The consistency (initial consistency) of the mixture is not particularly limited, but may be in the range of approximately 50 to 200. In some embodiments, the initial consistency of the mixture is, for example, 55 or higher, 60 or higher, or 65 or higher, preferably 70 or higher, more preferably 75 or higher, even more preferably 80 or higher, and particularly preferably 85 or higher (e.g., 90 or higher). For example, in the production of an insulating layer containing inorganic fibers, it is preferable that the initial consistency of the mixture is not too low, from the viewpoint of reducing fiber breakage of the inorganic fibers during the preparation, stirring, delivery, and coating of the mixture. Also, in some embodiments, the initial consistency of the mixture is preferably 180 or lower, more preferably 160 or lower, and even more preferably 140 or lower (e.g., 120 or lower or 110 or lower). It is advantageous that the initial consistency of the mixture is not too high, from the viewpoint of moldability when molding the mixture to obtain an insulating layer, and the shape accuracy of the molded product (insulating layer).

[0067] Regarding the method for measuring the consistency of the mixed liquid, the method described in Japanese Industrial Standard JIS K 2220:2013 "Grease - Part 7: Consistency Test Methods" is mentioned, and in particular, it is measured as "immiscibility consistency". Measuring instruments capable of measuring consistency are commercially available, specifically the PENETRO METER manufactured by Nichika Engineering. The measurement procedure involves preparing a pot of a size such that the cone-shaped weight does not come into contact with the mixture when it is lowered, filling it with the mixed liquid, and placing it in a measuring instrument to which the weight is attached. Next, the position of the weight is adjusted to a position where the weight and the mixed liquid come into contact, and this position is set as the zero point. Then, under room temperature conditions (25℃), the weight is lowered for 5 seconds (±0.1 seconds), and the consistency is calculated as the depth (mm) of the weight that entered the mixed liquid × 10. Furthermore, the cone-shaped weight should be a standard cone as defined in the Japanese Industrial Standards, with a total mass of 102.5g ± 0.05g and a weight holder mass of 47.5g ± 0.05g.

[0068] The coating method and conditions in the coating process are not particularly limited, and known methods can be used as appropriate. For example, coating can be done using a comma coater, spin coater, die coater, roll coater, calender roll, dispenser, etc.

[0069] The molding method and molding conditions in the molding process are not particularly limited, and known methods can be used as appropriate. For example, compression molding can be performed using a hot press or vacuum press, and drying can be performed using a floating oven, IR oven, etc. The drying temperature is preferably 60°C to 150°C. The drying time is preferably 4 to 20 minutes.

[0070] (Shape and characteristics of the insulation layer, etc.) The thickness of the insulation layer is not particularly limited and may be, for example, about 0.3 mm to 10 mm, preferably 0.5 mm or more, and may be 0.7 mm or more, 0.8 mm or more, or 0.9 mm or more. From the viewpoint of insulation performance and strength, a larger thickness of the insulation layer is advantageous. In some embodiments, the thickness of the insulation layer may be, for example, 1.0 mm or more, 1.2 mm or more, 1.5 mm or more, or 2.0 mm or more. Also, in some embodiments, the thickness of the insulation layer may be, for example, 9.0 mm or less, preferably 7.0 mm or less, more preferably 5.0 mm or less, and may be 3.0 mm or less, 2.0 mm or less, 1.5 mm or less, or 1.3 mm or less, or 1.0 mm or less. By reducing the thickness of the insulation layer, the insulation material can be made thinner and lighter. Furthermore, the thickness of the insulation layer can be determined by taking measurements of the cross-section of the insulation layer at several points (for example, 10 points) using a thickness measuring instrument (for example, a digital thickness gauge JAN-257 (measuring probe Φ20mm) manufactured by Ozaki Seisakusho) and using the average value obtained.

[0071] The density of the insulation layer is not particularly limited; for example, 0.2 g / cm³ 3 ~0.5g / cm 3It may be within the range described above. When the density of the insulating layer is within the above range, it becomes easier to ensure good thermal insulation and appropriate compressive deformation. In some embodiments, the density of the insulating layer is preferably 0.3 g / cm³. 3 More preferably 0.35 g / cm³ 3 More preferably 0.37 g / cm³ 3 The above applies, and preferably 0.45 g / cm³. 3 The following applies:

[0072] The shape of the insulation layer is not particularly limited. In some embodiments, the shape of the insulation layer when viewed from above may be, for example, a polygon such as a quadrilateral, a circle, an ellipse, etc. An example of a quadrilateral is a rectangle (including squares and rectangles).

[0073] The thermal conductivity of the insulation layer can be measured by the method described in Japanese Industrial Standard JIS A 1412-2:1999 "Method for measuring the thermal resistance and thermal conductivity of thermal insulating materials - Part 2: Heat flow meter method (HFM method)".

[0074] The heat flow metering method (HFM method) is a secondary or comparative measurement method that measures heat transfer characteristics such as thermal conductivity and thermal resistance by comparing a flat plate-shaped thermal insulating material (insulating layer), which is the test specimen, with a standard plate. The detailed measurement procedure and conditions are described below.

[0075] The insulation layer is cut to a predetermined size (e.g., 20mm x 20mm) to serve as a test specimen, and a standard plate is prepared, for example, an alumina composite material ("RS-100", manufactured by ZIRCAR Refractory Composites, Inc., thickness: 5mm, thermal conductivity: 0.66W / K·m). Next, the first thermocouple, titanium plate, insulation layer, titanium plate, second thermocouple, standard plate, and third thermocouple are placed on the lower plate of the pneumatic press in that order from top to bottom, and the test specimen, standard plate, thermocouples, etc. are placed in close contact with the upper and lower plates. Then, the upper and lower plates are heated to the predetermined measurement temperature, and a load is applied to the test specimen etc. using the pneumatic press to achieve the predetermined measurement pressure.

[0076] For example, the measurement temperatures can be set to 80°C for the upper plate on the first thermocouple side and 30°C for the lower plate on the third thermocouple side. On the other hand, for high-temperature conditions, the measurement temperatures can be set to 600°C for the upper plate on the first thermocouple side and 40°C for the lower plate on the third thermocouple side.

[0077] Furthermore, the measurement pressure can be, for example, 2 MPa (load: 800 N). While heated and pressurized, the measurement is continued until the detection temperature of each thermocouple stabilizes. From the detection temperature of each thermocouple after temperature stabilization, the thickness of the insulation layer when pressurized, the thermal conductivity of the standard plate, and the thickness of the standard plate when pressurized, the thermal conductivity k1 of the insulation layer can be calculated using the following formula (I). k1=k2×(L1×ΔT1) / (L2×ΔT2) ···(I) (In the formula, k1 is the thermal conductivity of the insulating layer [W / (m·K)], k2 is the thermal conductivity of the standard plate [W / (m·K)], L1 is the thickness of the insulating layer when pressed, L2 is the thickness of the standard plate, ΔT1 is the temperature difference between the temperature of the second thermocouple and the temperature of the third thermocouple, and ΔT2 is the temperature difference between the temperature of the first thermocouple and the temperature of the second thermocouple.) Note that the detection temperature being stable means, for example, that the temperature change around 10 minutes is within a predetermined range (for example, within ±0.1℃).

[0078] The thermal resistance of the insulation layer can be calculated from the aforementioned thermal conductivity k1 and the thickness L1 under pressure using the following formula (II). R1 = L1 / k1 ... (II) (In the formula, R1 is the thermal resistance of the insulating layer [(m 2 [·K) / W], where k1 is the thermal conductivity of the insulation layer [W / (m·K)], and L1 is the thickness of the insulation layer under pressure.

[0079] The thermal conductivity of the insulating layer disclosed herein under 600°C and 2MPa pressure conditions is preferably 0.3 W / K·m or less, more preferably 0.2 W / K·m or less, and more preferably 0.1 W / K·m or less. In some embodiments, the above thermal conductivity (600°C, 2MPa) is preferably 0.070 W / K·m or less, more preferably 0.065 W / K·m or less, even more preferably 0.060 W / K·m or less (e.g., less than 0.060 W / K·m), may be 0.059 W / K·m or less, or 0.058 W / K·m or less or 0.057 W / K·m or less. The lower limit of the thermal conductivity (600°C, 2MPa) of the insulating layer is not particularly limited, and a lower value is advantageous from the viewpoint of improving thermal insulation performance. In some embodiments, taking into consideration the balance with other characteristics, the thermal conductivity of the insulating layer (600°C, 2 MPa) may be, for example, 0.010 W / K·m or more, or 0.030 W / K·m or more.

[0080] The thermal resistance of an insulating layer prepared to have an initial thickness of 2 mm under 600°C and 2 MPa pressure conditions is, for example, 0.010 (K·m). 2 ) / W or more, preferably 0.014 (K·m) 2 ) / W or more or 0.015 (K·m 2 The thermal resistance of the insulation layer (2mm, 600℃, 1MPa) is greater than or equal to ) / W. There is no particular upper limit on the thermal resistance of the insulation layer (2mm, 600℃, 1MPa), and a lower value is advantageous from the viewpoint of improving insulation performance. In some embodiments, considering the balance with other properties and suitability for thinning, the thermal resistance of the insulation layer (2mm, 600℃, 2MPa) is, for example, 0.1 (K·m). 2 ) / W or less, and 0.5(K·m 2 ) / W or less or 0.3 (K·m 2 ) / W may be less than or equal to W.

[0081] The thermal conductivity of the insulating layer under 80°C and 2MPa pressure conditions is usually appropriate to be 0.3 W / K·m or less, preferably 0.1 W / K·m or less, more preferably 0.08 W / K·m or less, 0.06 W / K·m or less, 0.055 W / K·m or less, 0.045 W / K·m or less, or 0.04 W / K·m or less, and may also be, for example, 0.010 W / K·m or more.

[0082] Furthermore, in thermal insulation materials that include a buffer layer in addition to the thermal insulation layer, it is preferable that the thermal conductivity of the thermal insulation layer is lower than that of the buffer layer under at least one of the above conditions: 80°C, 2 MPa pressure or 600°C, 2 MPa pressure. In some embodiments, the thermal conductivity of the thermal insulation layer may be, for example, 90% or less, 75% or less, or 50% or less of the thermal conductivity of the buffer layer.

[0083] When the thickness of the insulation layer is prepared to be 2 mm when not pressurized (initial thickness), the thermal resistance under 80°C and 2 MPa pressurization conditions is, for example, 0.020 (K·m). 2 ) / W or more, preferably 0.025 (K·m) 2 ) / W or more, 0.03(K m 2 ) / W or more or 0.035 (K·m 2 ) / W or more, and also, for example, 0.1 (K·m 2 It is less than or equal to ) / W.

[0084] The compressive properties of the thermal insulation layer constituting the thermal insulation material disclosed herein are not particularly limited and can be appropriately selected depending on the application and manner of use. In some embodiments, the compressive deformation ratio of the thermal insulation layer at a compressive stress of 2.0 MPa (hereinafter also referred to as the 2.0 MPa compressive deformation ratio) is usually appropriate to be approximately 5% or more, preferably 8% or more, and more preferably 10% or more (e.g., 12% or more). Furthermore, the 2.0 MPa compressive deformation ratio of the thermal insulation layer may be, for example, 50% or less, and from the viewpoint of shape stability and mechanical strength, in some embodiments it may be 30% or less, more preferably 25% or less, for example 20% or less, and may also be 18% or less or 16% or less. By having the 2.0 MPa compressive deformation ratio of the thermal insulation layer within an appropriate range, it becomes easier to obtain appropriate compressive properties in the thermal insulation material including the thermal insulation layer, as described later. The 2.0 MPa compressive deformation ratio of the thermal insulation layer is measured as the compressive strain [%] when the compressive stress becomes 2.0 MPa in a compression test in which the thermal insulation layer is compressed in the thickness direction, and more specifically it is measured by the method described in the examples below.

[0085] The compression characteristics of the thermal insulation material are not particularly limited and can be appropriately selected depending on the application and manner of use. In some embodiments, the 2.0 MPa compression deformation ratio of the thermal insulation material is usually appropriate to be in the range of approximately 5% to 70% (e.g., 10% to 60%). By having an appropriate 1.0 MPa compression deformation ratio of the thermal insulation material, it is possible to appropriately buffer the expansion of cells (e.g., expansion due to charging) in thermal insulation material placed between cells of a lithium-ion battery module, for example. From the viewpoint of exhibiting better buffering performance, in some embodiments, the 2.0 MPa compression deformation ratio of the thermal insulation material is preferably 15% or more, more preferably 20% or more, and may be 25% or more, or 30% or more. Furthermore, from the viewpoint of facilitating the thinning of the thermal insulation material, in some embodiments, the above 2.0 MPa compression deformation ratio may be, for example, 55% or less, 50% or less, 45% or less, or 40% or less. The 2.0 MPa compression deformation ratio of the thermal insulation material is measured as the compressive strain [%] when the compressive stress becomes 2.0 MPa in a compression test in which the thermal insulation material is compressed in the thickness direction. In an insulating material consisting of an insulating layer, the 2.0 MPa compressive deformation ratio of the insulating material is the same as the 2.0 MPa compressive deformation ratio of the insulating layer.

[0086] The number of insulating layers contained in the insulating material is one or more, usually one to ten, preferably one to seven, and more preferably one to five (for example, one to three, or one to two).

[0087] The insulation layer may or may not be joined to the adjacent layer by an adhesive or bonding agent. In some embodiments, it is preferable that it is not joined by an adhesive or bonding agent. By not joining by an adhesive or bonding agent, i.e., by not using an adhesive or bonding agent, the thermal conductivity can be reduced compared to when such an agent is used.

[0088] <Coating layer> The thermal insulation material disclosed in this specification preferably includes a coating layer. The coating layer is a layer that suppresses the shedding of inorganic particles and other elements from the thermal insulation layer and protects the thermal insulation layer. For example, a coating layer made of a resin film may be preferably used.

[0089] The type of resin that constitutes the coating layer is not particularly limited. Specific examples of resins used in the coating layer include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyimide (PI), flame-retardant polycarbonate (PC), permeable porous polyethylene (PE), flame-retardant polyethylene (PE), and biaxially oriented nylon film (Ny). For permeable porous PE, a molecular weight of 1 million to 7 million is preferred.

[0090] The thickness of the coating layer is not particularly limited, but is, for example, 0.001 mm to 0.2 mm, preferably 0.005 mm or more, more preferably 0.007 mm or more, even more preferably 0.010 mm or more, and also preferably 0.15 mm or less, more preferably 0.10 mm or less, and even more preferably 0.050 mm or less. When the thickness of the coating layer is within the above range, both low thermal conductivity and mechanical strength can be achieved. The thickness of the coating layer can be measured in the same manner as the thickness of the heat insulating layer.

[0091] The number of coating layers is usually one or more, preferably two or more, usually five or less, preferably four or less, and even more preferably three or less. The two or more coating layers may be two or more resin films, or a single resin film may be folded to form two coating layers. In this case, the number of coating layers is considered to be two.

[0092] If the insulation material includes two or more coating layers, the two or more coating layers may enclose the insulation layer from the thickness direction, and the gap between these coating layers (the space partitioned by the two or more coating layers) may be sealed. The method for sealing the gap between the coating layers is not particularly limited, but for example, a method in which a sealing portion is provided on the outer edge of the coating layer and the sealing portions between opposing coating layers are bonded together. The method for bonding the sealing portions is also not particularly limited, and for example, welding using heat welding, ultrasonic welding, etc., or bonding using adhesives, adhesives, etc. Furthermore, welding may be performed by directly welding the resin of the coating layer, or by providing a separate resin layer for welding and then welding.

[0093] The coating layer may be joined to adjacent layers other than the coating layer (e.g., an insulating layer, a buffer layer, etc.) by an adhesive or bonding agent, or it may not be joined by an adhesive or bonding agent. In some embodiments, it is preferable that it is not joined by an adhesive or bonding agent.

[0094] In the thermal insulation materials disclosed herein, the thermal insulation layer may be covered in a breathable manner by two or more covering layers, or it may be sealed within a space partitioned by these covering layers. In some embodiments, it is preferable that the covering layers cover the thermal insulation layer in a breathable manner. The method for achieving the above breathable covering is not particularly limited. For example, methods such as using a covering layer having through holes as vents, or providing a non-sealed portion that functions as a vent at a part of the joint of two or more covering layers, can be employed individually or in appropriate combinations. Typically, the above vents are provided so as to connect the inside of the covering layer (thermal insulation layer side) with the external space. Thermal insulation materials in which the thermal insulation layer is covered in a breathable manner by covering layers have good deformability due to the breathability of the covering layers, and for example, compressive deformation due to volume expansion of cells is easily achieved.

[0095] The number of vents in the coating layer is usually 1 or more, preferably 2 or more, usually 50 or less, preferably 25 or less, and even more preferably 10 or less.

[0096] The total opening area of ​​the ventilation holes in the coating layer is typically 7.9 × 10 -5 cm 2 ~10cm 2 It is appropriate, preferably 1 × 10 -4 cm 2 The above is more comfortable 5x10 -3 cm 2 More preferably 1 × 10 -2 cm 2 The above, and preferably 5 cm 2 More preferably 4cm 2 Further preferably 3 cm 2 The following applies: If the total opening area of ​​the ventilation holes in the coating layer is within the above range, it is easier to suppress the outflow of powder from the insulation layer.

[0097] The vents in the coating layer may be covered with a ventilation membrane. The ventilation degree of the ventilation membrane is typically 4 cm. 3 / (cm 2 ·s) ~500cm 3 / (cm 2 It is appropriate that it be s), preferably 7cm 3 / (cm 2 s) or more, more preferably 10cm 3 / (cm 2 • s) More preferably 21 cm or more 3 / (cm 2 • s) or more, and preferably 250 cm 3 / (cm 2 • s) Preferably 200cm 3 / (cm 2 • s) Less than or equal to 100 cm, more preferably 100 cm 3 / (cm 2 •s) Below

[0098] <Buffer layer> The thermal insulation material disclosed herein may include layers other than the aforementioned thermal insulation layer and coating layer. An example of such a layer is a buffer layer. The buffer layer may play a role in supplementing physical properties that are often lacking in the thermal insulation layer alone. The buffer layer will be described in detail below.

[0099] In some embodiments, a buffer layer made of a fiber-containing molded article (hereinafter sometimes abbreviated as "fiber-containing article") or a buffer layer made of a foam-containing molded article (hereinafter sometimes abbreviated as "foam-containing article") may be preferably used.

[0100] (Fiber molded body) The type of fiber contained in the fibrous molded article is not particularly limited and may be inorganic or organic fiber. Examples of inorganic fibers include glass wool, rock wool, alkali earth silicate (AES) fiber, silica-alumina fiber, alumina fiber, zirconia fiber, silica fiber, basalt fiber, etc. Examples of organic fibers include cellulose fiber, polyester, polypropylene, felt, etc. In some embodiments, inorganic fibers are preferred, and glass wool is particularly preferred. Glass wool is a cured product containing fibers and a thermosetting resin (e.g., phenol binder), in which the fibers are joined together by the thermosetting resin. It also has the effect of increasing compressive stress and exhibiting a buffering function. The fibrous molded article may contain one type of fiber or two or more types of fibers. The aggregate form of the fibers may be a nonwoven fabric, woven fabric, knitted fabric, etc., and may be a nonwoven fabric, for example.

[0101] The fiber content in the fiber molded article is not particularly limited, but is, for example, 50% by mass or more (typically 50% to 99% by mass), preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more (for example 82% by mass or more), and also preferably 97% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less. When the fiber content is within the above range, the fiber molded article tends to exhibit cushioning properties.

[0102] The average fiber length of the fibers in the fibrous molded body is not particularly limited and may be, for example, in the range of 0.1 mm to 200 mm. In some embodiments, the average fiber length is preferably 1 mm or more (e.g., 5 mm or more), more preferably 10 mm or more, even more preferably 20 mm or more, and also preferably 175 mm or less, more preferably 150 mm or less, even more preferably 125 mm or less, and may be 100 mm or less, 75 mm or less, or 50 mm or less. When the average fiber length of the fibers is within the above range, it is easier to exhibit appropriate cushioning properties.

[0103] The average fiber diameter of the fibers in the fibrous molded article is not particularly limited and may be, for example, in the range of 1 μm to 15 μm. In some embodiments, the average fiber diameter is typically 2 μm or more, for example 2.5 μm or more, and may be 3 μm or more, or 4 μm or more. Also, in some embodiments, the average fiber diameter is typically 10 μm or less, for example 9 μm or less, and may be 8 μm or less, 7 μm or less, 6 μm or less, or 5 μm or less. When the average fiber diameter of the fibers is within the above range, the fibrous molded article is more likely to achieve both cushioning and low thermal conductivity.

[0104] The fibrous molded article preferably contains a binder (binding agent) in addition to the fibers. The type of binder in the fibrous molded article is not particularly limited, but it may be an organic binder or an inorganic binder.

[0105] Examples of organic binders include thermoplastic resins, thermoplastic elastomers, thermosetting resins, thermosetting elastomers, sugars, and water-soluble polymers. Examples of inorganic binders include aluminum oxide, zirconium oxide, magnesium oxide, titanium oxide, and calcium oxide. When the binder is one of the above, the shape stability is improved. Binders can be used individually or in combination of two or more types.

[0106] The binder content in the fibrous molded article is not particularly limited, and is, for example, 1% to 50% by mass of the fibrous molded article, preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and may be 10% by mass or more or 12% by mass or more, and also preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and may be 18% by mass or less or 16% by mass or less. When the binder content is within the above range, low thermal conductivity and good buffering properties are obtained.

[0107] In some embodiments, the fibrous molded article serving as a buffer layer preferably contains fibers but does not contain hydrophilic fumed silica. The fibrous molded article may, for example, be a molded article containing fibers but not containing inorganic particles. Furthermore, in some embodiments, the fibrous molded article serving as a buffer layer preferably contains fibers and a binder but does not contain hydrophilic fumed silica. The fibrous molded article may, for example, be a molded article containing fibers and a binder but not containing inorganic particles. Note that some fibers used in fibrous molded articles are sold with a thermosetting resin as a binder dispersed in them (attached to at least a portion of the fibers), and such fibers can be cut into the desired shape and then heated and compressed to form a fibrous molded article.

[0108] (Foam molded product) A foamed molded article is a molded article comprising a foam. The material of the foam is usually a resin such as a thermoplastic resin or a thermosetting resin. The foam can be molded by appropriately employing known molding methods and conditions.

[0109] The type of resin used to make up the foamed molded product is not particularly limited. Specific examples include foamed foams formed from resins such as polyethylene, polypropylene, other polyolefin resins, polyethylene terephthalate resin, polyvinyl chloride (PVC), polystyrene, polyurethane, resol-type phenolic resins (PF), melamine resins (MF), and epoxy resins (EP).

[0110] The cell structure of the foamed molded article may be closed-cell, open-cell, a mixture of both, or an intermediate cell structure. The cell structure of the foamed molded article can be appropriately selected according to the desired physical properties.

[0111] (Thickness of the buffer layer) If the thermal insulation material includes a buffer layer, the thickness of the buffer layer is usually 0.5 to 10 mm, but preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and also preferably 7 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less. When the thickness of the buffer layer is within the above range, it can adequately buffer the stress generated by the expansion of the battery (for example, expansion due to cell charging). The thickness of the buffer layer is measured in the same way as the thermal insulation layer by measuring the thickness of the cross-section of the buffer layer using a thickness measuring instrument (digital thickness gauge JAN-257, measuring probe Φ20 mm, manufactured by Ozaki Seisakusho), and the average value of the numerical group obtained by performing this measurement at any 10 locations is adopted.

[0112] (Compression characteristics of the buffer layer) The compressive modulus (yield point stress / strain) of the buffer layer is, for example, about 0.5 MPa to 20 MPa, preferably 0.7 MPa or higher, more preferably 0.9 MPa or higher, even more preferably 1.1 MPa or higher, and also preferably 18 MPa or lower, more preferably 16 MPa or lower, and even more preferably 14 MPa or lower.

[0113] When the compressive strain of the buffer layer is 25%, the compressive stress is, for example, 0.1 MPa to 4 MPa, preferably 0.2 MPa or more, more preferably 0.3 MPa or more, even more preferably 0.4 MPa or more, and also preferably 3.7 MPa or less, more preferably 3.5 MPa or less, and even more preferably 3.3 MPa or less. When the compressive strain of the buffer layer is 50%, the compressive stress is, for example, 0.3 MPa to 7 MPa, preferably 0.5 MPa or more, more preferably 0.6 MPa or more, even more preferably 0.7 MPa or more, and also preferably 6.5 MPa or less, more preferably 6.0 MPa or less, and even more preferably 5.5 MPa or less. When the compressive strain of the buffer layer is 70%, the compressive stress is, for example, 2 MPa to 15 MPa, preferably 2.3 MPa or more, more preferably 2.5 MPa or more, even more preferably 2.7 MPa or more, and also preferably 14 MPa or less, more preferably 12 MPa or less, and even more preferably 10 MPa or less.

[0114] The compressive stress and compressive modulus (yield point stress / strain) of the buffer layer can be measured using a precision universal testing machine such as an Autograph. Specifically, the buffer layer is cut to a predetermined size to form a test specimen (the cross-sectional area parallel to the plane perpendicular to the compression direction is used for calculating the compressive stress), and the compressive stress and displacement are measured when the test specimen is compressed at a predetermined compression rate (for example, 0.5 m / min) to calculate the compressive stress and displacement.

[0115] (Thermal properties of the buffer layer) The thermal conductivity of the buffer layer is not particularly limited. In some embodiments, the thermal conductivity of the buffer layer under conditions of 80°C and 1 MPa is, for example, 0.02 W / K·m or more, preferably 0.030 W / K·m or more, more preferably 0.040 W / K·m or more, even more preferably 0.050 W / K·m or more, and also preferably 0.2 W / K·m or less, more preferably 0.15 W / K·m or less, and even more preferably 0.1 W / K·m or less. Furthermore, the thermal conductivity of the buffer layer under conditions of 600°C and 1 MPa is preferably 0.04 W / K·m or more, more preferably 0.05 W / K·m or more, even more preferably 0.06 W / K·m or more, and also preferably 0.30 W / K·m or less, more preferably 0.25 W / K·m or less, and even more preferably 0.20 W / K·m or less. The thermal conductivity of the buffer layer can be measured by the same method as the method for measuring the thermal conductivity of the insulating layer.

[0116] The thermal resistance of the buffer layer is not particularly limited. In some embodiments, the thermal resistance of the buffer layer under conditions of 80°C and 1 MPa is preferably 0.020 (K·m). 2 ) / W or more, more preferably 0.025 (K·m) 2 ) / W or more, more preferably 0.03 (K·m) 2 ) / W or more, and preferably 0.07 (K·m) 2 ) / W or less, more preferably 0.06 (K·m) 2 ) / W or less, more preferably 0.05 (K·m) 2 The thermal resistance of the buffer layer under 600°C and 1MPa conditions is preferably 0.001 (K·m). 2 ) / W or more, more preferably 0.003 (K·m) 2 ) / W or more, more preferably 0.005 (K·m) 2 ) / W or more, and preferably 0.1(K·m) 2 ) / W or less, more preferably 0.05 (K·m) 2 ) / W or less, more preferably 0.01 (K·m) 2 ) / W or less. The thermal resistance of the buffer layer can be measured using the same method as the thermal resistance of the insulating layer.

[0117] The thermal resistance of a buffer layer prepared to have a thickness of 1 mm when not pressurized, under 80°C and 1 MPa conditions, is not particularly limited, but preferably 0.01 (K·m). 2 ) / W or more, more preferably 0.02 (K·m) 2 ) / W or more, more preferably 0.03 (K·m) 2 ) / W or more, and preferably 0.10(K·m) 2 ) / W or less, more preferably 0.09 (K·m) 2 ) / W or less, more preferably 0.08 (K·m) 2 ) / W or less. The thermal resistance of the buffer layer can be measured using the same method as the thermal resistance of the insulating layer.

[0118] The number of buffer layers is usually between 1 and 10, preferably between 1 and 5, and more preferably between 1 and 3, and may be 2 or 1.

[0119] The buffer layer may or may not be joined to the adjacent layer by an adhesive or adhesive. In some embodiments, it is preferable that it is not joined by an adhesive or adhesive. By not joining by an adhesive or adhesive, i.e., by not using an adhesive or adhesive, the increase in thermal conductivity can be suppressed compared to when such an adhesive is used.

[0120] The shape of the buffer layer is not particularly limited. In some embodiments, the shape of the buffer layer when viewed from above may be, for example, a polygon such as a quadrilateral, a circle, an ellipse, etc. An example of a quadrilateral is a rectangle (including squares and rectangles).

[0121] <Application> The applications of the thermal insulation materials disclosed herein are not particularly limited and can be used in any known application where thermal insulation materials are used. Some embodiments of the thermal insulation materials are preferably used as thermal insulation materials placed between cells of a battery module, and more specifically, are particularly preferably used as thermal insulation materials placed between cells of a lithium-ion battery module.

[0122] Figure 1 is a schematic perspective view showing an example of a battery module in which a heat insulating material is arranged between cells according to one embodiment, and Figure 2 is a cross-sectional view taken along line II-II. As shown in Figure 1, the battery module 50 comprises a plurality of battery cells (in this case, rectangular cells) 51 arranged in the thickness direction, with a heat insulating material 1 placed between each of the battery cells 51. The plurality of battery cells 51 arranged with the heat insulating material 1 in between are usually restrained with a pressing force (compressive force) applied in the thickness direction via restraining plates 52a, 52a located at both ends, and are housed in a battery case 53 for use.

[0123] As shown in Figure 2, the thermal insulation material 1 has a structure in which a thermal insulation layer 10 and a buffer layer 20 are laminated together and sandwiched from the thickness direction by two resin films (two coating layers) 31A and 31B. The resin films 31A and 31B are sealed by adhesion (e.g., heat welding) at sealing portions provided along their outer edges, and together form a coating material 30. When the thermal insulation material 1 with this structure is sandwiched between two adjacent battery cells 51, 51, it has the effect of insulating the space between the opposing surfaces 51a, 51a of the two battery cells 51, 51.

[0124] The following provides more specific examples of some possible forms of insulation materials. Figure 3 is a schematic cross-sectional view showing a thermal insulation material according to one embodiment. The thermal insulation material 1 shown in Figure 3 has a structure in which a thermal insulation layer 10 is laminated on one surface 20a of a buffer layer 20, and these are sandwiched and encased from the thickness direction by two resin films (two coating layers) 31A and 31B. The resin films 31A and 31B are sealed by adhesion (e.g., heat welding) at sealing portions 32 provided along their outer edges, and together form a coating material 30. The resin film 31A is molded into a convex shape that generally covers the end face of the laminate of the thermal insulation layer 10 and the buffer layer 20, and a ventilation opening (through hole) 33 is formed in the portion that covers this end face. A ventilation membrane 34 is placed at the opening of the ventilation opening 33 to the outside to prevent powder from flowing out from the thermal insulation layer.

[0125] Here, Figure 3 shows a configuration having only one insulation layer 10, but the number of insulation layers may be two or more. In a configuration with two or more insulation layers, these insulation layers may be arranged adjacent to each other, or separately, for example, on both sides of the buffer layer. Similarly, Figure 3 shows a configuration having only one buffer layer 20, but the number of buffer layers may be two or more. In a configuration with two or more buffer layers, these buffer layers may be arranged adjacent to each other, or separately, for example, on both sides of the insulation layer. Furthermore, the buffer layers may be arranged on the outside of the covering material, and two or more buffer layers may be arranged separately on the outside and inside of the covering material.

[0126] The target cells are not limited to rectangular cells; for example, laminated cells or cylindrical cells may also be used. The shape of the insulation material can be appropriately adopted depending on the type of cell.

[0127] Furthermore, the devices to which batteries are applicable include electric vehicles (EVs), hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), portable electronic devices such as mobile terminals, mobile phones and notebook computers, and wearable devices.

[0128] According to the technology disclosed herein, when preparing an insulating layer from a mixture (typically a slurry) containing silica particles in a solvent, the thermal conductivity of the resulting insulating layer can be suppressed even when water is used as the solvent in the mixture. This promotes the replacement of conventionally used organic solvents with water in the manufacture of the insulating layer and insulating materials containing the insulating layer, thereby reducing the amount of organic solvents used. Since many organic solvents are derived from natural resources such as petroleum, changing at least a portion of the organic solvents used in the manufacture of insulating layers to water is significant from the standpoint of sustainably managing and efficiently using natural resources. Furthermore, by changing from organic solvents to water, the amount of organic solvents released during the manufacture of the insulating layer can be reduced, thereby reducing the burden on the environment. In addition, solvent recovery equipment used to prevent the release of organic solvents into the atmosphere can be omitted or simplified, thus reducing the energy, such as electricity, required to operate the solvent recovery equipment. Moreover, by reducing the amount of organic solvents used, the energy required to manufacture the organic solvents themselves can be reduced. This improves the overall energy efficiency of the manufacture of insulating layers and insulating materials containing the insulating layer, contributing to more sustainable consumption and production.

[0129] As will be apparent from the above description and the following examples, the matters disclosed herein include the following: [1] Silica particles and, The following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A surfactant that satisfies the following conditions, An insulating material comprising an insulating layer containing, Here, the surface tension is the surface tension measured by the Dunou method using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The above light transmittance is the light transmittance measured by a spectrophotometer using an aqueous solution containing the above surfactant at a concentration of 1.1% by mass as the sample solution, in the context of an insulating material. [2] The thermal insulation material described in [1] above, wherein the HLB value of the surfactant is 10 or less. [3] The thermal insulation material according to [1] or [2] above, wherein the surfactant is a nonionic silicone-based surfactant. [4] The thermal insulation layer is the thermal insulation material according to any one of [1] to [3] above, comprising 0.01 to 15 parts by mass of the surfactant per 100 parts by mass of the silica particles. [5] The BET specific surface area of ​​the above silica particles is 80 m². 2 / g or more 400m 2 An insulating material described in any of the above [1] to [4], which is less than or equal to / g. [6] The thermal insulation material according to any of [1] to [5] above, wherein the silica particles are hydrophilic fumed silica. [7] The above-mentioned insulating layer is an insulating material according to any of [1] to [6] above, further comprising inorganic fibers. [8] A thermal insulation material according to any one of the above items [1] to [7], used in a battery module or battery pack that includes a plurality of arranged cells, by being placed between adjacent cells among the plurality of cells. [9] Silica particles and, The following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A surfactant that satisfies the following conditions, An insulating layer containing, Here, the surface tension is the surface tension measured by the Dunou method using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The above light transmittance is the light transmittance measured by a spectrophotometer using an aqueous solution containing the above surfactant at a concentration of 1.1% by mass as the sample solution, in the context of an insulating layer.

[10] Silica particles and the following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A mixing step in which a surfactant satisfying the requirements is mixed with an aqueous solvent to obtain a mixed solution; A coating step in which the above-mentioned mixture obtained in the above mixing step is applied to obtain a coating film; and, A molding step to obtain a heat insulating layer by molding the coated film obtained in the above coating step; A method for manufacturing thermal insulation materials, including the method described above.

[11] A method for producing an insulating material according to

[10] above, wherein the HLB value of the surfactant is 10 or less.

[12] The method for producing an insulating material according to

[10] or

[11] above, wherein the surfactant is a nonionic silicone-based surfactant.

[13] A method for producing an insulating material according to any of

[10] to

[12] above, wherein the amount of the surfactant in the above mixture is 0.05 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the above silica particles.

[14] A method for manufacturing an insulating material according to any one of

[10] to

[13] above, wherein the silica particles are hydrophilic fumed silica.

[15] The method for manufacturing an insulating material according to any one of

[10] to

[14] above, wherein the insulating layer further contains inorganic fibers. [Examples]

[0130] The following describes some embodiments of the present invention, but the present invention is not intended to be limited to those shown in these embodiments.

[0131] <Preparation of insulation material (insulation layer)> (Example 1) Hydrophilic fumed silica as silica particles (manufactured by Nippon Aerosil Co., Ltd., "AEROSIL® 200", average primary particle diameter: approximately 12 nm, BET specific surface area: 200 m²) 2A mixture was obtained by adding 100 parts by mass of silica particles (1 / g), 20 parts by mass of glass fiber (manufactured by Nitto Boseki Co., Ltd., "CS6J-888", average fiber length: 6 mm, average fiber diameter: 10.6 μm), and 5 parts by mass of surfactant A (modified silicone-based surfactant manufactured by Sunopco, trade name "SN Wet 125", nonionic, molecular weight 1340, decomposition onset temperature 300°C, HLB value 2.3, active ingredient content 100% by mass) to 435 parts by mass of water (surface tension: 73 mN / m) as a solvent and mixing. The amount of water used was set so that the total amount of silica particles and glass fiber was approximately 21% by mass of the entire mixture (the content of surfactant A per 100 parts by mass of solvent (water) was 1.1 parts by mass, i.e., the concentration in the solvent was 1.1% by mass). The mixture was applied to form a coating film with a thickness of 4 mm, resulting in a film with a thickness of 2 mm and a density of 0.3~0.5 g / cm³. 3 After compression molding the material into a sheet using a hot press, it was dried at 112°C for 10 minutes to produce the thermal insulation material (thermal insulation layer) described in this example.

[0132] (Example 2) An insulating material (insulating layer) according to this example was prepared in the same manner as in Example 1, except that surfactant B (a modified silicone-based surfactant manufactured by Sunopco, trade name "SN Deformer 1310", nonionic, molecular weight 4200, decomposition onset temperature 300°C, HLB value 2.3, active ingredient content 100% by mass) was used in place of surfactant A.

[0133] (Example 3) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 1, except that surfactant C (a silicone-based surfactant (polyether-modified polydimethylsiloxane) manufactured by BYK-Chemie, trade name "DISPER BYK-349", nonionic, with an active ingredient content of 100% by mass) was used in place of surfactant A.

[0134] (Example 4) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 1, except that surfactant D (a silicone-based surfactant (polyether-modified organosiloxane) manufactured by Shin-Etsu Silicone Co., Ltd., trade name "KF-643", nonionic, with an active ingredient content of 100% by mass) was used in place of surfactant A.

[0135] (Example 5) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 1, except that surfactant E (a modified silicone-based surfactant manufactured by Sunopco, trade name "SN Wet 126", nonionic, decomposition onset temperature 300°C, HLB value 2.2, active ingredient content 93% by mass) was used instead of surfactant A, and the amount used was 10 parts by mass per 100 parts by mass of silica particles (based on the amount of active ingredient).

[0136] (Example 6) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 5, except that the amount of surfactant E used (based on the amount of active ingredient) per 100 parts by mass of silica particles was set to 5 parts by mass.

[0137] (Comparative Example 1) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 1, except that surfactant F (a silicone-based surfactant manufactured by Kyoeisha Chemical Co., Ltd., trade name "Polyflow KL-100", nonionic, with an active ingredient content of 100% by mass) was used instead of surfactant A.

[0138] (Comparative Example 2) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 1, except that surfactant G (a silicone-based surfactant manufactured by Kyoeisha Chemical Co., Ltd., trade name "Polyflow KL-401", nonionic, with an active ingredient content of 100% by mass) was used instead of surfactant A.

[0139] (Comparative Example 3) The thermal insulation material (thermal insulation layer) according to this example was prepared in the same manner as in Example 1, except that surfactant A was not used.

[0140] The molecular weights of surfactants A and B described in the above examples and comparative examples are the weight-average molecular weights (Mw) based on GPC under the following conditions. The Mw values ​​of surfactants C to G based on GPC under the same conditions were all within the range of 1000 to 5000. In addition, the decomposition onset temperatures of surfactants A, B, and E described in the above examples and comparative examples are manufacturer's stated values, and the HLB values ​​are calculated values ​​based on the Kawakami method. Surfactants C, D, and G all have a decomposition onset temperature of 300°C or higher, and all have an HLB value of 10 or less. [GPC measurement conditions] Measuring device: TOSOH HLC-8320GPC (manufactured by Tosoh Corporation) Column: TSKgel SuperHZM-H / HZ4000 / HZ3000 / HZ2000 Column size: 6.0 mm I.D. × 150 mm Eluent:THF Flow rate: 0.6ml / min Detector: RI Column temperature: 40℃ Injection volume: 20μL Standard sample: Polystyrene

[0141] <Measurement and Evaluation> (Surface tension of surfactants) The surface tension of each surfactant was measured using a surface tension measuring device (product name "Wilhelmy type surface tension meter," manufactured by Kyowa Interface Science Co., Ltd.) based on the Dunouy method (ring method) described in JIS K3362:2008. Specifically, a 1.1% by mass aqueous solution of the surfactant to be measured (sample solution) was prepared, and approximately 50 mL of this sample solution was placed in a wide-mouth cup (volume 100 mL) for measurement, which was then placed on a stage provided by the apparatus. This stage is movable up and down. Next, the platinum ring (ring diameter 14.42 mm, ring wire diameter 0.40 mm) after acetone washing was suspended above the sample solution (with the surface of the platinum ring parallel to the surface of the sample solution). Then, at a temperature of 20°C, the platinum ring was briefly immersed in the sample solution and then raised relative to the sample solution (pre-wetting). Next, at a temperature of 20°C, the platinum ring was immersed in the sample solution, then raised relative to the sample solution. The peak value of the force acting on the ring (downward tensile force) when the platinum ring separated from the surface of the sample solution was measured, and the surface tension of the sample solution (1.1 mass% aqueous solution of surfactant) was determined from this measurement. The results are shown in Table 1. In this measurement, the stage ascent speed was set to 0.200 mm / second, the stage descent speed to 0.200 mm / second, the pre-wet stage ascent speed to 0.700 mm / second, the pre-wet stage descent speed to 0.700 mm / second, the pre-wet immersion distance to 2.5 mm, and the pre-wet immersion time to 5 seconds.

[0142] (Light transmittance of surfactants) The light transmittance of each surfactant at a wavelength of 400 nm was measured using a spectrophotometer (Shimadzu Corporation's UV-Vis spectrophotometer, product name "SolidSpec3700"). Specifically, a 1.1% by mass aqueous solution (sample solution) of the surfactant to be measured was prepared, set in the spectrophotometer, and the light transmittance in the wavelength range of 300 nm to 600 nm was measured so that the incident light was perpendicular to the cell containing the sample solution. From the obtained transmission spectrum, the transmittance at a wavelength of 400 nm was extracted. The results are shown in Table 1.

[0143] (Thermal conductivity of the insulation layer (600℃, 2MPa)) In accordance with the Japanese Industrial Standard JIS A 1412-2:1999 "Method for measuring the thermal resistance and thermal conductivity of thermal insulating materials - Part 2: Heat flow meter method (HFM method)", the thermal conductivity under conditions of 600°C and 1 MPa was measured as follows. First, a sample was prepared by cutting the insulating material (insulating layer) to a size of 20 mm x 20 mm. The above sample, a reference sample (alumina composite material ("RS-100", manufactured by ZIRCAR Refractory Composites, Inc., thickness: 5 mm, thermal conductivity: 0.66 W / (m·K))), and a titanium plate (thickness 0.2 mm) were prepared. On the lower plate of a pneumatic press (manufactured by Imoto Seisakusho Co., Ltd.), the following components were placed in order from top to bottom: thermocouple 1 (sheathed thermocouple K-type (SCHS1-0), φ=0.15, Class JIS1, manufactured by Chino Corporation), titanium plate, insulation material (sample) as a test specimen, titanium plate, thermocouple 2 (sheathed thermocouple K-type (SCHS1-0), φ=0.15, Class JIS1, manufactured by Chino Corporation), standard plate, and thermocouple 3 (sheathed thermocouple K-type (SCHS1-0), φ=0.15, Class JIS1, manufactured by Chino Corporation), ensuring that the insulation material, standard plate, thermocouples, etc., were in close contact. Next, the upper and lower plates were heated and adjusted so that the press load was 800N (equivalent to 2MPa), and then pressurized. Measurements were continued under heated and pressurized conditions until the thermocouple detection temperature stabilized. The heating temperatures were set to 600°C for the upper plate and 40°C for the lower plate. Furthermore, temperature stabilization was defined as a temperature change of within ±0.1°C around 10 minutes of continuous monitoring. The thermal conductivity k1 of the insulating material was determined from the detected temperature of each thermocouple after temperature stabilization, the thickness of the insulating material when compressed, and the thermal conductivity and thickness of the standard sample using the following equation (I). The results are shown in Table 1. k1=k2×(L1×ΔT1) / (L2×ΔT2) ···(I) (In the formula, k1 is the thermal conductivity of the insulation material [W / (m·K)], k2 is the thermal conductivity of the standard board [W / (m·K)], L1 is the thickness of the insulation material under pressure, L2 is the thickness of the standard board, ΔT1 is the temperature difference between the temperature of the second thermocouple and the temperature of the third thermocouple, and ΔT2 is the temperature difference between the temperature of the first thermocouple and the temperature of the second thermocouple.) The thermal resistance of each insulation material is calculated from the aforementioned thermal conductivity k1 and the thickness L1 under pressure using the following formula (II). R1 = L1 / k1 ... (II) (In the formula, R1 is the thermal resistance of the insulating layer [(m 2 [·K) / W], where k1 is the thermal conductivity of the insulation layer [W / (m·K)], and L1 is the thickness of the insulation layer under pressure.

[0144] (Compression deformation rate of the insulation layer) A compression test was performed using a precision universal testing machine (Autograph AGS-5kNX, manufactured by Shimadzu Corporation) to compress the thermal insulation material (insulation layer) at a compression speed of 0.5 mm / min. Compression strain [%] (compression displacement / initial thickness of the specimen) and compression stress [MPa] were measured. The compression strain at which the compression stress reached 2.0 MPa was read and adopted as the compression deformation rate of the thermal insulation material. As a result, the thermal insulation materials (insulation layers) of Examples 1 to 6 and Comparative Examples 1 to 3 all had an initial thickness of 2.0 mm and a thickness of 1.5 mm when pressurized at 2.0 MPa, and the compression deformation rate calculated from these was 25%.

[0145] (Nanopore count of the thermal insulation layer) The number of nanopores in the insulating layer was measured using a pore distribution analyzer (product name "Autopore V9620") manufactured by Micromeristics under the following conditions. The results are shown in Table 1. In the table, "ne" indicates that the measurement was not performed. [Measurement conditions] Sample: 0.05~0.08g (collected in a 5cc powder cell) Initial pressure: 2kPa Contact angle of mercury: 130 degrees Surface tension of mercury: 485 dynes / cm²

[0146] (Analysis of the amount of surfactant contained in the insulation layer) For Examples 2, 5, and 6 and Comparative Examples 1 and 2, the surfactant content in the obtained thermal insulation material (thermal insulation layer) was measured by liquid chromatography-mass spectrometry (LC / MS). First, standard solutions of multiple concentrations (based on the amount of active ingredient; the same applies hereinafter) containing the surfactant corresponding to each example were prepared, and a calibration curve was created between the surfactant concentration and the LC / MS area value. Next, 0.4 g of the thermal insulation layer was taken and the surfactant contained in the thermal insulation layer was extracted by adding it to 10 mL of methanol and shaking for more than 1 hour. The obtained solution was passed through a membrane filter (0.20 μm) and put into an LC / MS, and the surfactant content in the solution was measured from the calibration curve. From the surfactant content in 0.4 g of thermal insulation layer, the surfactant content in the thermal insulation layer was calculated, and the mass percentage of the surfactant remaining in the obtained thermal insulation layer out of the surfactant used to prepare the thermal insulation layer was determined. As a result, it was found that of the surfactants used to prepare the heat insulating layer, approximately 100% by mass remained in the obtained heat insulating layer in Example 2, approximately 74% by mass in Examples 5 and 6, approximately 68% by mass in Comparative Example 1, and approximately 100% in Comparative Example 2.

[0147] [Table 1]

[0148] As shown in Table 1, in a comparison of the thermal insulation materials (thermal insulation layers) of Examples 1-6 and Comparative Examples 1-3, which were manufactured using an aqueous solvent, Examples 1-6, which used surfactants A-E satisfying a surface tension of 15 mN / m to 30 mN / m and a light transmittance of 90% or less, clearly showed a greater effect in suppressing thermal conductivity compared to Comparative Example 3, which did not use a surfactant. A particularly high effect was observed in Examples 1-3. On the other hand, Comparative Example 1, which used surfactant E that did not satisfy the above light transmittance requirement, showed a smaller effect in suppressing thermal conductivity compared to Examples 1-6, and Comparative Example 2, which used surfactant F that did not satisfy either the above light transmittance or surface tension requirement, showed an even smaller effect. Furthermore, the values ​​for the nanopore count and thermal conductivity of the insulating layers in Examples 1-3, Example 6, and Comparative Example 3 clearly show a trend in that thermal conductivity decreases as the nanopore count increases. This result supports the hypothesis that the aggregation of silica particles (reduction in nanopore count) caused by using water instead of organic solvents during the manufacturing of the insulating layer contributes to the increase in thermal conductivity, and that suppressing the aggregation of silica particles and thus reducing the decrease in nanopore count by using an appropriate surfactant has the effect of suppressing the increase in thermal conductivity.

[0149] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. [Explanation of Symbols]

[0150] 1. Insulation 10. Insulation layer 20 Buffer layer 30 Covering material 31A Resin film 31B Resin film 32 Seal part 33 Ventilation holes 34. Ventilated membrane 50 Battery Modules 51 battery cells

Claims

1. Silica particles and The following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A surfactant that satisfies the following conditions, An insulating material comprising an insulating layer containing, Here, the surface tension is the surface tension measured by the Dunou method using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution. The aforementioned light transmittance is the light transmittance measured by a spectrophotometer using an aqueous solution containing the surfactant at a concentration of 1.1% by mass as the sample solution, in the present invention relates to an insulating material.

2. The thermal insulation material according to claim 1, wherein the HLB value of the surfactant is 10 or less.

3. The thermal insulation material according to claim 1, wherein the surfactant is a nonionic silicone-based surfactant.

4. The thermal insulation material according to any one of claims 1 to 3, wherein the thermal insulation layer contains 0.01 to 15 parts by mass of the surfactant per 100 parts by mass of the silica particles.

5. The BET specific surface area of ​​the silica particles is 80 m². ２ / g or more 400m ２ The thermal insulation material according to any one of claims 1 to 3, wherein the amount is less than or equal to / g.

6. The thermal insulation material according to any one of claims 1 to 3, wherein the silica particles are hydrophilic fumed silica.

7. The thermal insulation material according to any one of claims 1 to 3, wherein the thermal insulation layer further comprises inorganic fibers.

8. The thermal insulation material according to any one of claims 1 to 3, used in a battery module or battery pack including a plurality of arranged cells, by being placed between adjacent cells among the plurality of cells.

9. Silica particles and the following conditions: The surface tension is 15 mN / m or more and 30 mN / m or less; and, The light transmittance at a wavelength of 400 nm is 90% or less; A mixing step in which a surfactant satisfying the requirements is mixed in an aqueous solvent to obtain a mixed solution; A coating step in which the mixed solution obtained in the mixing step is applied to obtain a coating film; and, A molding step to obtain a heat insulating layer by molding the coated film obtained in the above coating step; A method for manufacturing thermal insulation materials, including the method described above.

10. The method for producing a heat insulating material according to claim 9, wherein the amount of the surfactant in the mixed liquid is 0.05 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the silica particles.

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